Week 4 - Volcanoes, Mount Redoubt, Alaska

Cook Inlet, Alaska

Illustration Credit:  USGS

       

While chartering a fishing trip out with my family in Alaska last year we happened to motor into Cook Inlet where our guide told us to look off to our left.  We got a good view of Mount Redoubt, a stratovolcano off the western shore of Cook Inlet in the southern part of Alaska.  Our guide then proceeded to give us a little history on what is still considered a very active volcano.  Having never seen a volcano before, we listened with rapt attention. 

  

 

Mount Redoubt, Alaska

Photo Credit:  USGS

 Our guide explained to us:

The last major eruption of Mount Redoubt occurred in 2009.  There have been four other eruptions since 1900 occurring in 1902, 1966, 1968, 1989-90. More modern telemetric seismic monitoring has alerted scientists of coming eruptions signaled often by many mini earthquakes. Historical data shows that the lava flows and pyroclastic flows (tephra) were largely andesitic because silicon dioxide compositions were in the 50-60 percentages with the 1966 and 1968 eruptions showing some dacitic tendencies with silica percentages in the high 60’s.   The gases from Mount Redoubt have been mostly water vapors with some of the gas venting through fumaroles on the side of the mountain (http://pubs.dggsalaskagov.us/webpubs/dggs/ri/text/ri2011_005.pdf). 

 Many lava domes have grown over the past century from moderately viscous flows of lava.  Since the lava was not extremely hot, the lava cooled relatively quickly after leaving the core and created these lava domes.  Mount Redoubt did create many mudslides because of the very quick melting of snow and glaciers in surrounding countryside and these lahars produced many safety concerns for inhabitants.  Pyroclastic flows of ash also created flight risks for pilots after the 1989-90 eruption that caused grounding of flights for some period of time (https://www.sciencedirect.com/science/article/abs/pii/0377027394900388). 

We all thoroughly enjoyed our guided fishing boat experience and caught many Coho salmon that day with my son catching the largest weighing 35 pounds (no photo available!).